Degreasing and coating apparatus and process



Jan. 2, 1962 P. R. HENDRIXSON ET AL DEGREASiNG AND COATING APPARATUS AND PROCESS I Filed May 15, 3.957

INVENTORS PHILIP R. HENDRIXSON FREDERICK G. SCHUMACHER ATTORNEY United States Patent Ofiice 3,015,576 Patented Jan. 2, 1962 3,015,576 DEGREASING AND COATING APPARATUS AND PROCESS Philip R. Hendrixson and Frederick G. Schumacher, Wilmington, Del., assignors to E. I du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed May 15, 1957, Ser. No. 659,355 2 Claims. (Cl. 117-49) This invention relates to an apparatus and process for the continuous, sequential degreasing and spray painting of articles by the use of volatile solvents. It relates particularly to an apparatus and process for the treatment of metal articles employing chlorinated hydrocarbon degreasing sol-vents.

Heretofore, de reasing and coating processes have usually been carried out as separate steps using separate treating equipment for each step. Furthermore, coating processes have been manipulated to avoid exposure of the freshly coated article with hot solvent vapor to prevent decoating. Borushko, U.S. Patent 2,728,686, accomplishes this by vapor degreasing then removing the article from the solvent vapor and dip coating by rapid immersion and withdrawal from a hot coating composition under a minimal solvent vapor zone. Bede, U.S. Patent 2,763,575, accomplishes spray coating by spraying the hot coating composition on articles maintained at normal atmospheric temperature. The prior art has indicated that sequential cleaning and painting in an atmosphere of hot solvent vapor, though economically desirable to minimize heat and solvent losses, would be inoperable.

The object of this invention is to provide an apparatus in which soiled metal parts can be cleaned and then subjected to a protective spray coating in a single processing unit in an atmosphere consisting of the vapor of a chlorinated degreasing solvent at its boiling point and at atmospheric pressure. Another object is to provide a sequential cleaning and coating process carried out by the apparatus as described. A further object is to provide a single processing unit for degreasing-coating operations in which heat and solvent losses are minimal. A still further objective is to provide an apparatus and process for the sequential cleaning, solvent treatment with corrosion inhibitors and spray painting with minimal loss of heat and solvent. An additional object is to provide a sequential cleaning and coating process as heretofore described employing a single non-inflammable chlorinated hydrocarbon degreasing solvent.

Various additional advantages of the invention will appear in the following description and schematic drawing.

The drawing presents a simple three dimensional side view of apparatus illustrating the features of this invention.

The apparatus as shown comprises a sheet metal treating vessel which contains the solvent, treating solutions and solvent vapors. The front side wall 20 of this vessel is shown partially removed to disclose its inner structure. This vessel is closed to exclude air and retain solvent vapor but is open or apertured at 11 and 12 to allow the introduction and removal of work. These openings are partially surrounded by cooling coils 48 to prevent loss of solvent vapor. The work 13 is carried through the treating vessel by means of a conveyor 14. The vessel as shown, consists of three sections 15, 16 and 17, separated by partitions 35 and 36. These sections contain hot solvent as shown and solvent vapor which rises to the vapor line 18. The first section, 15, serves to clean oily or greasy parts by use of standard degreasing techniques. In the second section, 16, the article is sprayed with paint in which the degreasing solvent is the solvent medium. In the third section, 17,

time is provided for the paint droplets to coalesce and thus form a uniform smooth coating. Evaporation of vehicle and run-off of surplus paint take place in this section. Additional sections may be introduced between the cleaning (15) and painting.(l6) sections for other treatments prior to painting. This may include treat ment with solvent containing a phosphorous acid derivative capable of inhibiting corrosion. The function of the individual sections will now be described in greater detail.

Section 15 may consist of one or more units depending upon the nature of the parts and the degree of soil. In the drawing, section 15, is divided into two solventcontaining units 22 and 23. Very dirty parts are dipped into the solvent as indicated by alternate conveyorroute, dotted line 24. The parts may also be subjected to a solvent spray, 19. Unit 23, is heated to the boiling point with steam coil 24 to generate solvent vapor. Unit 22 is not heated and, when trichlorethylene is the solvent, may be comparatively cool, approximately F. Pure solvent is returned to 22 from the work entrance condensate which is collected at 26 and returned through line 27 containing water separator 28. Solvent flows over Weir 30 separating units 22 and 23. A purge stream of dirty solvent is removed continuously through line 29 to a purification still. Pure or recovered solvent enters pump 25 through line 46 and is pumped through line 26 and sprayed at 19. Spray solvent may also be drawn from the condensate line 27 if desired.

The cleaned and preheated part passes by conveyor 14 from section 15 over partition 35 to section 16 where it is sprayed with paint 45 in which the degreasing solvent is the solvent medium. The paint is kept at its boiling point by heating with steam coil 31. It is pumped with pump 32 through line 33 including heat exchanger 34 and sprayed on the work at 21. The paint is preferably pumped under pressure and heated somewhat above its boiling point before passage through the spray orifice 21.

The painted article is now carried over partition 36 to section 17 where the paint film becomes smooth and excess paint drops 01f into the boiling solvent. External heating may be applied by infrared lamp or lamps 38 to dry paint while still in the solvent vapor atmosphere. Alternatively, induction heating may be used in place of infrared radiation if desired. Steam coil 39 keeps the solvent 37 boiling and solvent condensate is collected at 40 and returned to 37 through line 41, water being separated, if present, by separator 42. Fresh paint or pigment must be fed through line 43. Purge stream '44 is removed continuously from 37 for distillation recovery of solvent and excess paint which can be returned through line 43 to 45.

Numerous modifications of this apparatus will be obvious to anyone skilled in the art. While the preferred means in which the principles of the present invention may be embodied have been demonstrated, it is to be understood that the invention is not to be limited to the particular means shown and described. Widely different means may be employed in the practice of the broader aspects of the invention.

Having described the invention, we claim:

1. An apparatus for the continuous cleaning and coating of metal articles under solvent vapor comprising an elongated vessel having entrance and exit openings in the upper ends thereof, condensing means positioned below Said openings for defining a single and continuous airfree solvent vapor zone within said vessel below said openings, the bottom of said vessel being divided into a plurality of sections by partitions, said sections being adapted to contain hot solvent and solvent containing mixtures for sequential degreasing, spray painting, and

' degreasing section, a spray painting section, and a paint coalescing section comprising the steps of conveying the articles into said vapor zone, moving said articles in a horizontal path of uninterrupted immersion in said vapor zone, and thereby sequentially subjecting said articles to the degreasing section, the spray painting section Where 15 paint is being sprayed above its boiling point, and the coalescing section, adding heat to said articles in said coalescing section, and thereafter removing said articles from said zone.

References Cited in the file of this patent UNITED STATES PATENTS 486,744 Titzel Nov. 22, 1892 2,661,310 Page et a1 Dec. 1, 1953 2,728,686 Borushko Dec. 27, 1955 2,763,575 Bede Sept. 18, 1956 1 2,809,129 Peterson Oct.v8, 1957 Hendrixson Nov. 25, 1958 

1. AN APPARATUS FOR THE CONTINUOUS CLEANING AND COATING OF METAL ARTICLES UNDER SOLVENT VAPOR COMPRISING AN ELONGATED VESSEL HAVING ENTRANCE AND EXIT OPENINGS IN THE UPPER ENDS THEREOF, CONDENSING MEANS POSITIONED BELOW SAID OPENINGS FOR DEFINING A SINGLE AND CONTINUOUS AIRFREE SOLVENT VAPOR ZONE WITHIN SAID VESSEL BELOW SAID OPENINGS, THE BOTTOM OF SAID VESSEL BEING DIVIDED INTO A PLURALITY OF SECTIONS BY PARTITIONS, SAID SECTIONS BEING ADAPTED TO CONTAIN HOT SOLVENT AND SEOVENT CONTAINING 